The impact of pH and acid-activated proteases on the decrease of immunological properties of parvalbumin from freshwater fish

Abstract

Fermentation has been found as an effective method to decrease the hypersensitive reactions of consumers by freshwater fish, but the reason is not clear. Therefore, the aim of this study was to investigate the impact of pH and acid-activated proteases on the decrease of immunological properties of parvalbumin from freshwater fish, by the indicators of SDS-polyacrylamide gel electrophoresis, western blotting, enzyme-linked immunosorbent assay, surface hydrophobicity and circular dichroism. The results showed that black carp (Mylopharyngodon piceus) had the highest level of immunological properties reflected by quantitation, the content of linear epitopes and conformational epitopes of parvalbumin, and IgE-binding rate. Afterwards, purified parvalbumin from black carp was obtained with purity higher than 95%. Then, for acidification and enzyme models, it indicated that acid-activated proteases were the reason for the decrease of immunological properties. Ulteriorly, the mechanism on the level of protein structure was provided, which showed the decrease of α-helix and the increase of β-turn and random coil, as well as the decrease of surface hydrophobicity had joint contribution for the breaking of conformational epitopes. This study could provide a novel guidance for the decrease of immunological properties of fish and promote fish processing industry further.